This invention relates to neurological signal data acquisition systems, and particularly to devices which monitor electrical-neurological information and transmit representative information to a central location for analysis.
In the study of animal behavior and stimuli response, there is a desire to monitor the electrical-neurological signals referred to as synaptic response xe2x80x9cspikesxe2x80x9d, electroencephalographic (xe2x80x9cEGxe2x80x9d) signals, electromyographic (xe2x80x9cEMGxe2x80x9d) signals, or electrocardiographic (xe2x80x9cEKGxe2x80x9d) signals of mobile animals such as rats, mice, monkeys and fish in their natural environment. There also exists a desire to study the electrical-neurological signals of mobile human test subjects, without binding them to bulky, stationary test equipment or confining them to a laboratory. There is a further desire to study the electrical-neurological signals of human patients in remote locations, such as accident sites or battle-field environments. Previous approaches have had limited range dictated by wires or short range radio transmitters. Attempts to utilize radio transmitters have involved utilizing analog sensors, A-D converters, and digital transmitters to broadcast information to a central location. However, A-D conversion prior to transmission requires complex circuitry with relatively large size, weight, and power usage.
These previous approaches are found not to be practical for studying small test animals such as rats, mice and fish. Additionally, these previous approaches are too complex and bulky to operate in a non-laboratory environment, especially if numerous signals are required. A typical electrical-neurological signal acquisition system includes a probe connected to a buffer amplifier (pre-amp). These pre-amps are connected by long wires to differential amplifiers. Output from the differential amplifiers is passed through analog filters and processed by an A-D converter. Digitized data is then sent to a computer processor where it is placed in digital storage or displayed for human analysis.
One prior patent, John U.S. Pat. No. 6,052,619, describes a portable EEG instrument for use in emergencies and brain assessments. This portable EEG instrument replaced the long wires of a typical neurological data acquisition system with a digital transmitter. A headband containing one or a few EEG electrodes is placed on the head of the patient. The electrodes are connected to pre-amplifiers which are, in turn, connected to differential amplifiers. The output from the amplifiers is processed by an A-D converter. The digital information is then transmitted using a digital transmitter. A receiver unit is monitored by a trained individual. The receiver unit has a digital radio receiver with a demodulator, an amplifier and filters to separate demodulated signals into bands. A dial on the receiver unit is used to select a signal band and output the band to a speaker. The individual monitoring the speaker is trained to interpret output from the speaker representative of the electrical-neurological signals detected by the probes of the headband. The A-D converter and digital transmitter and receiver eliminate the need for wires to connect the detection equipment (probes, amplifiers) to the central analyzer (filter, dial, speaker). Information of interest is converted from A-D form prior to digital transmission at the location of the patient. This requires complex circuitry with associated size, weight and power requirements at the site of the patient. It would be desirable to move A-D conversion to the site of the central analyzer where size, weight, and power resources are not as constrained as at the remote patient location.
Accordingly, there is a need for a mobile electrical-neurological data acquisition system that is small and light enough to be worn by small test animals such as rats, mice, monkeys, and various fish in their natural environments and by human test subjects and patients away from a laboratory or hospital. There is also a need for a mobile electrical-neurological data acquisition system with a significant range (600-1000 feet) to monitor animals in their natural environment, monitor mobile human test subjects, and monitor patients in remote locations. An additional need exists for a mobile electrical-neurological data acquisition system that accepts numerous electrical-neurological signals from probes, amplifies the representative analog data signals, modulates a carrier wave with the analog data signals, and broadcasts the resulting modulated signal to a processing station. Yet another need exits for a processing station to receive a broadcast modulated signal, demodulate the analog data signals and convert the analog data signals to digital signals prior to digital storage or display for human analysis.
The present invention meets the aforementioned needs by connecting numerous electrical-neurological probes to amplifiers to produce amplified analog signal representations. The amplified signals are processed by a multiplexor to produce a combined analog signal that is modulated and broadcast using an analog transmitter. The modulating signal is encoded and applied to the transmitter so as to ensure that amplitude levels can be determined properly at the receiver. After reception and demodulation by an analog receiver, the combined analog signal is converted to a combined digital signal using an A-D converter (xe2x80x9cADCxe2x80x9d). To obtain the original electrical-neurological signal representations, a computer processor applies software algorithms to de-multiplex the combined digital signal. The result is a separate digital signal representation for each of the electrical-neurological signals monitored by the probes. The separate digital signals are available for human analysis or can be stored on a digital device such as a hard drive for later analysis.
Should the number of electrical-neurological signals be too numerous to combine using a single multiplexor, the signals can be processed in hierarchical stages. The amplified electrical-neurological signals are grouped into subsets, each subset being processed by a first level multiplexor to produce a first level combined signal. The first level combined signals are processed by a second level multiplexor to produce a second level combined signal, encompassing all electrical-neurological signals. The second level combined signal is modulated and broadcast using an analog transmitter. Likewise, additional levels can be added to accommodate even more electrical-neurological signals.
Accordingly, it is a principle object of the present invention to provide a novel and improved neurological signal data acquisition system and method.
It is another object of the present invention to provide a system and method for combined multiplexed analog representation of numerous electrical-neurological signals suitable for modulation and transmission by a single channel radio frequency analog transmitter.
It is a further object of the present invention to provide a system and method that receives the combined signal and produces therefrom a separate digital representation for each electrical-neurological signal monitored by the probes.
It is yet a further object of the present invention to provide a novel physical package for mounting a portion of a neurological signal data acquisition system on an animal or patient.